Relay of charging information for proximity services

ABSTRACT

Systems and methods for providing charging information for a device-to-device (D2D) communication. One embodiment is User Equipment (UE) that collects charging information for a D2D communication with one or more other UEs, to determine that the UE is out-of-coverage of a mobile network, to select a relay entity capable of relaying the charging information from the UE to the mobile network, and to transmit the charging information to the relay entity. The relay entity may then relay the charging information to the mobile network to initiate charging for the D2D communication.

FIELD OF THE INVENTION

The invention is related to the field of communication systems and, inparticular, to charging for proximity services.

BACKGROUND

Proximity services or proximity-based services refer to servicesprovided between devices (i.e., User Equipment (UE)) being in proximityto each other. Proximity services utilize the radio technologies of theUEs so that the UEs in close proximity can exchange communicationsdirectly with one another without going through the core network, whichis also referred to as device-to-device (D2D) communications. A UE isconsidered in “proximity” of another UE if they are able to establishdirect communications.

The Third Generation Partnership Program (3GPP) has defined ProximityServices (ProSe) for a Long Term Evolution (LTE) network. ProSe allowsfor D2D communications as an underlay to the cellular network. In D2Dcommunications, UEs transmit data signals to each other over a directlink using the cellular resources instead of routing the data signalsthrough the core network. Therefore, D2D communications involve directlytransmitting traffic between UEs that are in the vicinity of one anotherinstead of routing the traffic over a core network, such as the EvolvedPacket Core (EPC). Because there is direct communication between UEsthat are in close proximity, D2D communications offload traffic from theEPC network without additional infrastructure. D2D communications mayalso offer higher data rates, lower transfer delays, and better powerefficiency within a UE.

Proximity services generally include direct discovery, directcommunication, and UE-to-network relay. Direct discovery is a functionwhere a UE identifies other UEs that are in proximity Directcommunication is a function where UEs in proximity are able tocommunicate using local radio resources. UE-to-network relay is afunction where a UE can relay traffic from a remote UE to the network,or from the network to the remote UE. For example, if a UE (referred toas a remote UE) is outside of the coverage area of the base stations fora network, then the UE-to-network relay function allows the remote UE totransmit traffic to a relay UE that is in the coverage area of a basestation through a direct communication with the relay UE. The relay UEin turn forwards the traffic from the remote UE to the network bycommunicating with a base station of the network.

SUMMARY

Embodiments described herein provide an offline charging mechanism forD2D communications. A UE involved in a D2D communication collectscharging information for the D2D communication. When the UE isout-of-coverage of the mobile network and cannot directly forward thecharging information to the mobile network, the UE is able to forwardthe charging information to a relay entity that does have a connectionwith the network. The relay entity may then relay the charginginformation for the D2D communication to the mobile network. Thus, eventhough the UE is out-of-coverage of the mobile network, it is able toprovide the charging information to an offline charging system for themobile network through the relay entity. The offline charging mechanismmay then initiate charging for the D2D communication.

One embodiment comprises a UE having a radio interface configured toexchange over-the-air signals, and a charging controller. The chargingcontroller is configured to collect charging information for a D2Dcommunication with one or more other UEs. The charging controller isconfigured to determine that the UE is out-of-coverage of a mobilenetwork, and to select a relay entity capable of relaying the charginginformation from the UE to the mobile network. The radio interface isconfigured to transmit the charging information to the relay entity.

In another embodiment, the relay entity comprises a relay UE, and theradio interface is configured to transmit the charging information tothe relay UE in a signaling message over a control channel.

In another embodiment, the charging controller is configured to receivea control message from the mobile network when the UE is in-coverage ofthe mobile network indicating a default relay identity for the UE, andto select the relay entity based on the default relay identity when theUE goes out-of-coverage of the mobile network.

In another embodiment, when multiple relay entities are available to theUE, the charging controller is configured to select one of the relayentities that has a connection with a Wireless Local Area Network(WLAN).

In another embodiment, when multiple relay entities are available to theUE, the charging controller is configured to select one of the relayentities based on signal strength between the UE and the relay entities.

In another embodiment, when multiple relay entities are available to theUE, the charging controller is configured to select one of the relayentities that is in-coverage of the mobile network.

In another embodiment, when multiple relay entities are available to theUE, the charging controller is configured to select one of the relayentities based on a number of hops from each of the relay entities tothe mobile network.

In another embodiment, the charging information is for multiple D2Dcommunications involving the UE.

Another embodiment comprises a method for providing charging informationfor a D2D communication. The method includes collecting charginginformation in a UE for a D2D communication with one or more other UEs,determining that the UE is out-of-coverage of a mobile network,selecting a relay entity capable of relaying the charging informationfrom the UE to the mobile network, and transmitting the charginginformation from the UE to the relay entity.

Another embodiment is a relay entity having a connection with a mobilenetwork. The relay entity includes a radio interface configured toreceive charging information for a D2D communication involving a UE thatis out-of-coverage of the mobile network. The relay entity also includesa charging relay controller configured to identify a routing address torelay the charging information, and to relay the charging information tothe routing address.

In another embodiment, the charging relay controller is configured torelay the charging information to the mobile network through a WLAN.

In another embodiment, the radio interface is configured to receive thecharging information from the UE in a signaling message over a controlchannel.

In another embodiment, the charging relay controller is configured torelay the charging information to the mobile network through a RAN.

In another embodiment, the relay entity comprises relay UE that isin-coverage of the RAN of the mobile network.

In another embodiment, the charging relay controller is configured tostore a pre-provisioned network address for a Charging Trigger Function(CTF) for which to send the charging information.

Another embodiment comprises a method of relaying charging informationin a relay entity having a connection with a mobile network. The methodincludes receiving charging information for a D2D communicationinvolving a UE that is out-of-coverage of the mobile network,identifying a routing address to relay the charging information, andrelaying the charging information to the routing address.

The above summary provides a basic understanding of some aspects of thespecification. This summary is not an extensive overview of thespecification. It is intended to neither identify key or criticalelements of the specification nor delineate any scope of the particularembodiments of the specification, or any scope of the claims. Its solepurpose is to present some concepts of the specification in a simplifiedform as a prelude to the more detailed description that is presentedlater.

DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are now described, by way of exampleonly, and with reference to the accompanying drawings. The samereference number represents the same element or the same type of elementon all drawings.

FIG. 1 illustrates an architecture of a mobile network for ProSefeatures in an LTE network

FIG. 2 illustrates direct communication scenarios between two UEs.

FIG. 3 illustrates a relay scenario in an exemplary embodiment.

FIG. 4 is a schematic diagram of a mobile network illustrating a relayfunction used for offline charging in an exemplary embodiment.

FIG. 5 illustrates a UE that provides charging information in anexemplary embodiment.

FIG. 6 illustrates a relay entity in an exemplary embodiment.

FIG. 7 is a flow chart illustrating a method for providing charginginformation for a D2D communication in an exemplary embodiment.

FIG. 8 is a flow chart illustrating a method for relaying the charginginformation to a mobile network in an exemplary embodiment.

DESCRIPTION OF EMBODIMENTS

The figures and the following description illustrate specific exemplaryembodiments. It will thus be appreciated that those skilled in the artwill be able to devise various arrangements that, although notexplicitly described or shown herein, embody the principles of theembodiments and are included within the scope of the embodiments.Furthermore, any examples described herein are intended to aid inunderstanding the principles of the embodiments, and are to be construedas being without limitation to such specifically recited examples andconditions. As a result, the inventive concept(s) is not limited to thespecific embodiments or examples described below, but by the claims andtheir equivalents.

FIG. 1 illustrates an architecture of a mobile network 100 (e.g., PublicLand Mobile Network (PLMN)) for ProSe features in an LTE network.Architecture 100 is described in 3GPP TS 23.303 (v12.0.0), which isincorporated by reference as if fully included herein. Architecture 100includes an Evolved Packet Core (EPC) network 110 that communicates withUEs 120-121 over a Radio Access Network (RAN), which is illustrated asan Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) 112. Althoughnot shown in FIG. 1, E-UTRAN 112 includes a plurality of base stations(e.g., eNodeB) that provide wireless connections between UEs 120-121(and other UEs) and EPC network 110. EPC network 110 includes a MobilityManagement Entity 114, an S-GW 115, and a P-GW 116, but may includeother elements not shown. The operation of these elements in EPC network110 is outside of the scope of the embodiments described herein.Architecture 100 also includes a Home Subscriber Server (HSS) 117 and aSecure User Plane Location Platform (SLP) 118, which are also beyond thescope of the embodiments.

The architecture 100 in FIG. 1 illustrates a non-roaming scenario.However, there may be other architectures applicable to the embodimentsdescribed herein, such as an inter-PLMN architecture (see FIGS. 4.2-2 of3GPP TS 23.303), a roaming architecture (see FIGS. 4.2-3 of 3GPP TS23.303), an architecture when a UE is covered by a WLAN instead of anE-UTRAN, etc.

Architecture 100 further includes a Proximity Service (ProSe) function130 and a ProSe Application Server (AS) 132. ProSe function 130comprises any server, device, apparatus, or equipment (includinghardware) that is used for network-related actions required forproximity services. ProSe function 130 may play different roles for eachof the features of a proximity service. ProSe AS 132 comprises anyserver, device, apparatus, or equipment (including hardware) thatsupports storage of EPC ProSe User IDs and ProSe Function IDs, andmapping of Application Layer User IDs and EPC ProSe User IDs.

UEs 120-121 comprise any devices used directly by an end user forcommunication, such as a mobile terminal, a laptop computer equippedwith a mobile broadband adapter, etc. UEs 120-121 may be considered asProSe-enabled, meaning that they support ProSe requirements andassociated procedures. A ProSe-enabled UE as described herein refers toboth a non-Public Safety UE and a Public Safety UE. Each UE 120-121includes an application 122 and 123, respectively, that is used toaccess/provide proximity services (e.g., ProSe), such as D2D directcommunication and UE-to-network relay. The applications 122-123 maycomprise a local voice service, multimedia content sharing, gaming,group multicast, content-aware applications, public safety, etc.

Although 3GPP ProSe is discussed above for architecture 100, this isjust one example. The concepts discussed herein are applicable to anyproximity service that enables direct communication between end userdevices. Proximity services as discussed herein include the followingfunctions: discovery, direct communication (D2D), and UE-to-networkrelay. Discovery is a process that identifies a UE in proximity of otherUEs. One type of discovery is direct discovery, which is a processemployed by a UE to discover other UEs in its vicinity by using only thecapabilities of the two UEs. For example, one UE may use local radioresources to discover the presence of other UEs in its vicinity. Anothertype of discovery is referred to as EPC-level discovery, which is aprocess by which EPC network 110 determines the proximity of two UEs andinforms them of their proximity. For example, a server in EPC network110 may monitor the location of UEs, and inform the UEs of theirproximity.

Direct communication is a communication between two or more UEs inproximity by means of user data plane transmission using radiotechnology (e.g., E-UTRA) via a channel not traversing any network node(other than possibly a base station of a RAN). Direct communicationallows the UEs to use local radio resources to communicate directly witheach other without routing traffic through a core network, such as EPCnetwork 110. For example, UEs may directly communicate through the radioresources available to both UEs from a RAN, such as from a base station.UEs may also directly communicate through the radio resources of the UEsthemselves, such as over the PC5 reference point. Either way, thetraffic exchanged between the UEs is not routed through the corenetwork, but is routed directly between the UEs over a wirelessinterface.

FIG. 2 illustrates direct communication scenarios between two UEs. Inscenario 201, a base station 206 is in communication with UEs 210-211.Base station 206 communicates with UEs 210-211 over the control plane(also referred to as control path or control channel) to exchangesignaling messages and other types of control messages with UEs 210-211.UEs 210-211 are able to establish a direct communication over a userdata plane (also referred to as a data path or data channel) using localradio resources to communicate directly with each other without routingtraffic through a core network. In scenario 202, base station 206 againcommunicates with UEs 210-211 over the control plane to exchangesignaling messages and other types of control messages with UEs 210-211.UEs 210-211 are able to establish a direct communication over the userdata plane through base station 206 without routing traffic through acore network. In each of the above scenarios, UEs 210-211 establish adirect communication between each other, which is also referred toherein as a D2D communication.

UE-to-network relay is a function where one UE provides functionality tosupport connectivity to “unicast” services for one or more remote UEs. Aremote UE refers to a UE that is not served by a RAN (e.g., E-UTRAN),and communicates with a Packet Data Network (PDN) through aUE-to-network relay. For instance, if a remote UE is out-of-coverage ofa RAN, then the remote UE may still access the PDN through another UE(relay UE) that is in-coverage of the RAN. A relay UE is a device thatis enabled for UE-to-network relay. UE-to-network relay allows forone-to-one or one-to-many communications from the network to a remote UEvia a relay UE which is in-coverage, or from a remote UE to the networkvia a relay UE that is in-coverage. Therefore, the term “UE-to-networkrelay” refers to communication from a remote UE to the network, and fromthe network to the remote UE. The communication between a remote UE anda relay UE, or between two relay UEs, is referred to as a directcommunication or D2D communication.

The embodiments described herein apply to a relay function for proximityservices. FIG. 3 illustrates a relay scenario in an exemplaryembodiment. In the relay scenario, a remote UE 302 is out-of-coverage ofa RAN but has communication with a relay entity 304. In turn, relayentity 304 has a connection with a core network 308. Relay entity 304comprises any device that is able to act as a relay for a UE that isout-of-coverage of a RAN. The term “out-of-coverage” refers to a UE thatis outside of the coverage area of any base station of a RAN for amobile network. A RAN refers to the air interface and base stationtechnology in a cellular network, one example of which is an E-UTRAN.The term “in-coverage” refers to a UE that is in the coverage area of abase station of a RAN.

Relay entity 304 may comprise a relay UE that is enabled forUE-to-network relay. For instance, a relay UE may be in-coverage of abase station (e.g., eNodeB) of a mobile network, and is enabled to relayunicast traffic (UL and DL) between remote UE 302 and core network 308.Relay entity 304 may alternatively comprise a relay device of a WirelessLocal Area Network (WLAN), such as a WLAN router. A WLAN links two ormore devices using a wireless distribution method (e.g., Wi-Fi orWi-MAX), and typically provides a connection through an access point tothe packet data network, such as the Internet. A relay device of a WLANis able to communicate with remote UE 302, and relay traffic from remoteUE 302 to core network 308.

FIG. 4 is a schematic diagram of a mobile network 400 illustrating arelay function used for offline charging in an exemplary embodiment.Mobile network 400 includes a base station 402 that has a coverage area404 (or service area) representing a cell. In this embodiment, UE 410may represent a relay UE for a UE-to-network relay function. UE 410 iswithin the coverage area 404 of base station 402, so UE 410 isconsidered in-coverage of base station 402. UE 410 is enabled forrelaying of charging information from a remote UE to mobile network 400.

UE 412 and UE 414 have established a D2D communication. In other words,UE 412 and UE 414 performed a discovery function, and have initiated adirect communication with one another. UE 412 is not within the coveragearea 404 of base station 402, but does have communication capabilitywith UE 410 that is within the coverage area 404 of base station 402. UE412 may have service through the same service provider as UE 410, orthey may have different service providers.

Mobile network 400 also includes a proximity service function 430 and anoffline charging system (OFCS) 440. Proximity service function 430comprises a server, device, apparatus, or equipment (including hardware)that is used for network-related actions required for proximityservices. One example of proximity service function 430 is a ProSefunction defined by the 3GPP. Proximity service function 430 includes aCharging Trigger Function (CTF) 432. A CTF is a component that detectschargeable events for services, assembles information for the chargeableevents into matching charging events, and sends the charging events toan OFCS (e.g., a Charging Data Function (CDF)).

OFCS 440 comprises a server, device, apparatus, or equipment (includinghardware) that provides offline charging for services provided in mobilenetwork 400. OFCS 440 may include a Charging Data Function and ChargingGateway Function (CDF/CGF) 442. A CDF comprises an element or modulewithin an OFCS that receives charging events from CTFs within networkelements, formats the charging events into CDRs, and sends the CDRs to aCGF. A CGF comprises an element or module within an OFCS that correlatesCDRs for a session, and forwards a CDR file with the correlated CDRs toa billing domain.

There may be intervening network elements between base station 402 andproximity service function 430 that are not shown for the sake ofbrevity, such as a Serving Gateway (SGW) or Packet Data Network Gateway(PGW) of an LTE network.

FIG. 4 also shows a WLAN device 450 of a WLAN 452 as part of mobilenetwork 400. WLAN device 450 comprises a device, apparatus, or equipment(including hardware) that communicates with a UE through wirelesssignals. One example of WLAN device 450 is a WiFi router. In thisembodiment, WLAN device 450 is able to communicate with proximityservice function 430 through WLAN 452, and is enabled to act as a relayfor charging information from a UE to proximity service function 430.

For this embodiment, UE 412 and UE 414 engage in a D2D communication. AUE that is part of a D2D communication, such as UE 412, is enhanced toprovide charging information for the D2D communication to mobile network400 through a relay function. Also, a relay entity, such as UE 410 orWLAN device 450, is enhanced to route charging information for a D2Dcommunication to mobile network 400.

FIG. 5 illustrates UE 412 that provides charging information in anexemplary embodiment. UE 412 is enabled for proximity services, and isenhanced to provide charging information to mobile network 400 even whenUE 412 is out-of-coverage of mobile network 400 (i.e., out-of-coverageof base station 402). UE 412 includes a charging controller 502(including a processor) and a radio interface 504. Charging controller502 is configured to send charging information for a D2D communicationto a mobile network through a relay entity. Radio interface 504represents the local radio resources of UE 412, such as a transceiverand an antenna, used for wireless communications to exchangeover-the-air signals. Any UE involved in a D2D communication may have asimilar configuration as UE 412.

FIG. 6 illustrates a relay entity 600 in an exemplary embodiment. Relayentity 600 may represent UE 410 in FIG. 4, WLAN device 450, or any otherdevice enabled for relay functions. Relay entity 600 includes a chargingrelay controller 602 (including a processor) and a radio interface 604.Charging relay controller 602 is configured to route charginginformation from an out-of-coverage UE to a mobile network through arelay function. Radio interface 604 represents the local radio resourcesof relay entity 600, such as a transceiver and an antenna, used forwireless communications to exchange over-the-air signals.

FIG. 7 is a flow chart illustrating a method 700 for providing charginginformation for a D2D communication in an exemplary embodiment. Thesteps of method 700 will be described with reference to UE 412 in FIG.5, but those skilled in the art will appreciate that method 700 may beperformed in other systems. Also, the steps of the flow charts describedherein are not all inclusive and may include other steps not shown, andthe steps may be performed in an alternative order.

Charging controller 502 in UE 412 collects charging information for theD2D communication with UE 414 and/or other UEs not shown (step 702). Thecharging information includes any data used to perform offline chargingfor the D2D communication. For example, the charging information mayinclude an application ID, a session ID, a charging ID, timestamps(e.g., start and end of D2D communication), etc. The charginginformation may be for a single D2D communication, or multiple D2Dcommunications involving UE 412. After collecting the charginginformation, charging controller 502 may temporarily store the charginginformation, such as in a local memory.

Charging controller 502 determines that UE 412 (i.e., the radiointerface 504 of UE 412) is out-of-coverage of mobile network 400 (step704). As shown in FIG. 4, UE 412 is out-of-coverage of base station 402(and other base stations of mobile network 400), so charging controller502 is able to determine that UE 412 is out-of-coverage of mobilenetwork 400. Because UE 412 is out-of-coverage of mobile network 400, itcannot send the charging information directly to mobile network 400.Therefore, charging controller 502 selects a relay entity capable ofrelaying the charging information from UE 412 to mobile network 400(step 706). There may be multiple relay entities available to chargingcontroller 502 from which to select, and charging controller 502 mayselect one of the relay entities in a variety of ways. In oneembodiment, charging controller 502 may select one of the relay entitiesthat has a connection with WLAN 452, such as WLAN device 450. Forexample, if one of the relay entities has a connection with a WLAN andother relay entities are in-coverage of the RAN (i.e., base station402), then charging controller 502 may select the relay entity having aconnection with the WLAN instead of the relay entities in-coverage ofthe RAN.

In another embodiment, charging controller 502 may select one of therelay entities based on signal strength between UE 412 and the relayentities. For example, if there are multiple relay entities in-coverageof the RAN, then charging controller 502 may select the relay entitywhich has the strongest signal with UE 412.

In another embodiment, charging controller 502 may select one of therelay entities based on a number of hops from each of the relay entitiesto mobile network 400. A hop or degree of separation may indicate thenumber of D2D links that are established between a relay UE and anotherrelay UE that is in-coverage of a base station. For example, UE 410 isin-coverage of base station 402, so UE 412 would have zero hops to relayUE 410. If UE 412 did not have direct communication with UE 410 (that isin-coverage) but had D2D communication with UE 410 through another relayUE (not shown in FIG. 4), then UE 412 would have 1 hop (e.g., one D2Dlink) to UE 410. Charging controller 502 may select the relay entityhaving the least number of hops to mobile network 400.

In another embodiment, charging controller 502 may receive a defaultrelay identity from mobile network 400. Although UE 412 isout-of-coverage as shown in FIG. 4, UE 412 is mobile and may have beenin-coverage of mobile network 400 at an earlier time. When UE 412 wasin-coverage, charging controller 502 may receive a control message frommobile network 400 indicating a default relay identity for UE 412. Forexample, the default relay identity may be an identifier or address forUE 410, WLAN device 450, or another relay entity. Charging controller502 may select the relay entity based on the default relay identity whenUE 412 goes out-of-coverage of mobile network 400, as shown in FIG. 4.

A relay entity, such as a relay UE, may be a non-participant in the D2Dcommunication indicated in the charging information. For example, inFIG. 4, UE 410 is not a participant in the D2D communication for whichthe charging information pertains. Therefore, UE 410 would act as anon-participating relay UE. There may be instances where the relay UEmay be a participant in the D2D communication, and also act as a relayUE for one or more other participants in the D2D communication that areout-of-coverage. For example, if UE 414 were in-coverage of mobilenetwork 400, then UE 414 could act as a participating relay UE for UE412.

After selecting the relay entity, radio interface 504 transmits thecharging information to the relay entity (step 708 of FIG. 7). Radiointerface 504 may transmit the charging information in different waysdepending on which relay entity is selected. If the relay entity is arelay UE (e.g., relay UE 410), then radio interface 504 may transmit thecharging information in a signaling message over the control channel. Asignaling message is a type of message used for mobility management,authentication, security, session management, etc. The control channelmay use Non-Access Stratum (NAS) protocol or another protocol.

Radio interface 504 may alternatively set up a data channel (i.e., a D2Dcommunication) with the relay UE through signaling messages, andtransmit the charging information over the data channel. If the relayentity is a WLAN device (e.g., WLAN device 450), then radio interface504 may establish a data channel (i.e., a WiFi communication) with theWLAN device, and transmit the charging information over the datachannel.

After UE 412 transmits the charging information to the relay entity, therelay entity operates to relay the charging information to mobilenetwork 400. FIG. 8 is a flow chart illustrating a method 800 forrelaying the charging information to mobile network 400 in an exemplaryembodiment. The steps of method 800 will be described with reference torelay entity 600 in FIG. 6, but those skilled in the art will appreciatethat method 800 may be performed in other systems.

Radio interface 604 of relaying entity 600 receives the charginginformation for the D2D communication (step 802). In response toreceiving the charging information, charging relay controller 602identifies a routing address to relay the charging information (step804). Charging relay controller 602 may be pre-provisioned with arouting address for the charging information. For example, chargingrelay controller 602 may store a network address for a Charging TriggerFunction (CTF) in mobile network 400 that is configured to generate acharging event for the D2D communication. The CTF may be in proximityservice function 430 (see CTF 432 in FIG. 4), in an application server(not shown in FIG. 4), or some other network element. The CTF willcollect the charging information, assemble the charging information intoa matching charging event, and send the charging event to OFCS 440.Charging relay controller 602 may also query a device in mobile network400 (or another mobile network), such as a Home Subscriber Server (HSS),for a routing address to relay the charging information.

Charging relay controller 602 then relays the charging information tothe routing address (step 806). Relay entity 600 may therefore relay thecharging information received from UE 412 to mobile network 400. Forexample, if relay entity 600 is UE 410, then UE 410 may forward thecharging information to proximity service function 430 through basestation 402. If relay entity 600 is WLAN device 450, then WLAN device450 may forward the charging information to proximity service function430 through WLAN 452. Relay entity 600 may also relay the charginginformation to another relay entity.

The content of the charging information may vary as desired. In a 3GPPProSe example, the charging information discussed above may include thefollowing data:

-   -   ProSe Application ID    -   ProSe Application Code    -   ProSe Filter ID    -   ProSe Event/Session ID    -   ProSe Charging ID (optional. It could be pre-configured when UE        has access to ProSe Function via any connection protocols)    -   Discovery Models (Model A/B or Discoverer/Discoveree)    -   ProSe Discovery Role Types    -   Direct Communication Types (One-to-One or One-to-Many)    -   Subscriber Identifier    -   Subscriber ProSe Mode (Transmitter or Receiver)    -   Number of Recipients    -   Subscriber PLMN ID    -   ProSe Function ID    -   Subscriber Location Information    -   Served Network Type (=non-E-UTRAN)    -   ProSe timestamps    -   Other charging fields defined in 3GPP TS 32.299.

After the charging information is routed to CTF 432, for example, CTF432 triggers a charging event toward OFCS 440 (see FIG. 4). For example,CTF 432 may generate a Diameter Rf Accounting Request (ACR) based on thecharging information received for the D2D communication, and transmitthe Diameter ACR to OFCS 440. CDF/CGF 442 may process the Diameter ACRto generate a CDR.

UE 414 may operate in a similar fashion to provide charging informationfor the D2D communication to mobile network 400. In the case of UE 414,it is also out-of-coverage of mobile network 400, so it may select arelay entity to relay the charging information to mobile network 400. UE412 may operate as a relay entity in this example to relay the charginginformation to UE 410. UE 410 in turn may operate as a relay entity torelay the charging information to mobile network 400 (through basestation 402).

The above embodiments advantageously allow a UE that is/was involved ina D2D communication(s) to send charging information to a mobile networkeven though the UE is out-of-coverage of the mobile network. Therefore,the UE does not have to store the charging information for an extendedperiod of time until it is in-coverage of the mobile network, and themobile network does not need to wait to initiate charging. The charginginformation could be lost if the UE is forced to store the charginginformation for an extended period of time, which results in lostrevenue for the operator of the mobile network.

Any of the various elements or modules shown in the figures or describedherein may be implemented as hardware, software, firmware, or somecombination of these. For example, an element may be implemented asdedicated hardware. Dedicated hardware elements may be referred to as“processors”, “controllers”, or some similar terminology. When providedby a processor, the functions may be provided by a single dedicatedprocessor, by a single shared processor, or by a plurality of individualprocessors, some of which may be shared. Moreover, explicit use of theterm “processor” or “controller” should not be construed to referexclusively to hardware capable of executing software, and mayimplicitly include, without limitation, digital signal processor (DSP)hardware, a network processor, application specific integrated circuit(ASIC) or other circuitry, field programmable gate array (FPGA), readonly memory (ROM) for storing software, random access memory (RAM),non-volatile storage, logic, or some other physical hardware componentor module.

Also, an element may be implemented as instructions executable by aprocessor or a computer to perform the functions of the element. Someexamples of instructions are software, program code, and firmware. Theinstructions are operational when executed by the processor to directthe processor to perform the functions of the element. The instructionsmay be stored on storage devices that are readable by the processor.Some examples of the storage devices are digital or solid-statememories, magnetic storage media such as a magnetic disks and magnetictapes, hard drives, or optically readable digital data storage media.

Although specific embodiments were described herein, the scope of thedisclosure is not limited to those specific embodiments. The scope ofthe disclosure is defined by the following claims and any equivalentsthereof.

We claim:
 1. An apparatus comprising: User Equipment (UE) comprising: aradio interface configured to exchange over-the-air signals; and acharging controller configured to collect charging information for adevice-to-device (D2D) communication with at least one other UE, todetermine that the UE is out-of-coverage of a mobile network, and toselect a relay entity capable of relaying the charging information fromthe UE to the mobile network; the radio interface is configured totransmit the charging information to the relay entity.
 2. The apparatusof claim 1 wherein: the relay entity comprises a relay UE; and the radiointerface is configured to transmit the charging information to therelay UE in a signaling message over a control channel.
 3. The apparatusof claim 1 wherein: the charging controller is configured to receive acontrol message from the mobile network when the UE is in-coverage ofthe mobile network indicating a default relay identity for the UE, andto select the relay entity based on the default relay identity when theUE goes out-of-coverage of the mobile network.
 4. The apparatus of claim1 wherein: when multiple relay entities are available to the UE, thecharging controller is configured to select one of the relay entitiesthat has a connection with a Wireless Local Area Network (WLAN).
 5. Theapparatus of claim 1 wherein: when multiple relay entities are availableto the UE, the charging controller is configured to select one of therelay entities based on signal strength between the UE and the relayentities.
 6. The apparatus of claim 1 wherein: when multiple relayentities are available to the UE, the charging controller is configuredto select one of the relay entities that is in-coverage of the mobilenetwork.
 7. The apparatus of claim 1 wherein: when multiple relayentities are available to the UE, the charging controller is configuredto select one of the relay entities based on a number of hops from eachof the relay entities to the mobile network.
 8. The apparatus of claim 1wherein: the charging information is for multiple D2D communicationsinvolving the UE.
 9. A method comprising: collecting charginginformation in User Equipment (UE) for a device-to-device (D2D)communication with at least one other UE; determining that the UE isout-of-coverage of a mobile network; selecting a relay entity capable ofrelaying the charging information from the UE to the mobile network; andtransmitting the charging information from the UE to the relay entity.10. The method of claim 9 wherein transmitting the charging informationfrom the UE to the relay entity comprises: transmitting the charginginformation to the relay entity in a signaling message over a controlchannel.
 11. The method of claim 9 wherein selecting a relay entitycomprises: receiving a control message from the mobile network when theUE is in-coverage of the mobile network indicating a default relayidentity for the UE; and selecting the relay entity based on the defaultrelay identity when the UE goes out-of-coverage of the mobile network.12. The method of claim 9 wherein selecting a relay entity comprises:when multiple relay entities are available to the UE, selecting one ofthe relay entities that has a connection with a Wireless Local AreaNetwork (WLAN).
 13. The method of claim 9 wherein selecting a relayentity comprises: when multiple relay entities are available to the UE,selecting one of the relay entities based on signal strength between theUE and the relay entities.
 14. The method of claim 9 wherein selecting arelay entity comprises: when multiple relay entities are available tothe UE, selecting one of the relay entities that is in-coverage of themobile network.
 15. The method of claim 9 wherein selecting a relayentity comprises: when multiple relay entities are available to the UE,selecting one of the relay entities based on a number of hops from eachof the relay entities to the mobile network.
 16. The method of claim 9wherein: the charging information is for multiple D2D communicationsinvolving the UE.
 17. An apparatus comprising: a relay entity having aconnection with a mobile network, the relay entity comprising: a radiointerface configured to receive charging information for adevice-to-device (D2D) communication involving User Equipment (UE) thatis out-of-coverage of the mobile network; and a charging relaycontroller configured to identify a routing address to relay thecharging information, and to relay the charging information to therouting address.
 18. The apparatus of claim 17 wherein: the chargingrelay controller is configured to relay the charging information to themobile network through a Wireless Local Area Network (WLAN).
 19. Theapparatus of claim 17 wherein: the radio interface is configured toreceive the charging information from the UE in a signaling message overa control channel.
 20. The apparatus of claim 17 wherein: the chargingrelay controller is configured to relay the charging information to themobile network through a Radio Access Network (RAN).
 21. The apparatusof claim 20 wherein: the relay entity comprises a relay UE that isin-coverage of the RAN of the mobile network.
 22. The apparatus of claim17 wherein: the charging relay controller is configured to store apre-provisioned network address for a Charging Trigger Function (CTF)for which to send the charging information.
 23. A method comprising:receiving, in a relay entity having a connection with a mobile network,charging information for a device-to-device (D2D) communicationinvolving User Equipment (UE) that is out-of-coverage of the mobilenetwork; identifying a routing address to relay the charginginformation; and relaying the charging information to the routingaddress.
 24. The method of claim 23 wherein relaying the charginginformation comprises: relaying the charging information to the mobilenetwork through a Wireless Local Area Network (WLAN).
 25. The method ofclaim 23 wherein receiving the charging information comprises: receivingthe charging information from the UE in a signaling message over acontrol channel.
 26. The method of claim 23 wherein relaying thecharging information comprises: relaying the charging information to themobile network through a Radio Access Network (RAN).